linux-kernel - RE: [PATCH 1/3] zram: force disksize setting before using zram

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Date:	Fri, 18 Jan 2013 12:19:17 -0800 (PST)
From:	Dan Magenheimer <dan.magenheimer@...cle.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Minchan Kim <minchan@...nel.org>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Nitin Gupta <ngupta@...are.org>,
	Seth Jennings <sjenning@...ux.vnet.ibm.com>,
	Konrad Rzeszutek Wilk <konrad@...nok.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: RE: [PATCH 1/3] zram: force disksize setting before using zram

> From: Greg Kroah-Hartman [mailto:gregkh@...uxfoundation.org]
> Sent: Thursday, January 17, 2013 5:42 PM
> To: Minchan Kim
> Cc: linux-mm@...ck.org; linux-kernel@...r.kernel.org; Nitin Gupta; Seth Jennings; Dan Magenheimer;
> Konrad Rzeszutek Wilk; Jerome Marchand; Pekka Enberg
> Subject: Re: [PATCH 1/3] zram: force disksize setting before using zram
> 
> On Thu, Jan 17, 2013 at 11:12:47AM +0900, Minchan Kim wrote:
> > Now zram document syas "set disksize is optional"
> > but partly it's wrong. When you try to use zram firstly after
> > booting, you must set disksize, otherwise zram can't work because
> > zram gendisk's size is 0. But once you do it, you can use zram freely
> > after reset because reset doesn't reset to zero paradoxically.
> > So in this time, disksize setting is optional.:(
> > It's inconsitent for user behavior and not straightforward.
> >
> > This patch forces always setting disksize firstly before using zram.
> > Yes. It changes current behavior so someone could complain when
> > he upgrades zram. Apparently it could be a problem if zram is mainline
> > but it still lives in staging so behavior could be changed for right
> > way to go. Let them excuse.
> 
> I don't know about changing this behavior.  I need some acks from some
> of the other zram developers before I can take this, or any of the other
> patches in this series.

I'm not officially a zram developer, but I have used it and I
am knowledgeable about in-kernel compression and know the specific
problem being fixed here.  Unless/until compression is much
more tightly integrated into MM policies and "z*" can manage
space more dynamically, Minchan's patch seems to be a good way
to go, especially since zram has found a solid niche in the
embedded (no swap disk) community.  So FWIW:

Acked-by: Dan Magenheimer <dan.magenheimer@...cle.com>
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